Biomedical subjects

A V Shafirkin

Publications and source records attributed to A V Shafirkin.

At least 19 recordsLinked to original sources

PubMed2004

[Radiation risk to cosmonauts in a flight to Mars].

The paper presents results of the 14-year studies (1966-1980) with dogs irradiated by presumable doses of the galactic cosmic rays (GCR) and solar cosmic rays (SCR) that might affect cosmonauts during a flight to Mars. Along with data of chronic experiments with small laboratory animals exposed to a broad variety of dose rates, our data formed a basis for construction of mathematical models of processes of radiation damage to living organisms, and growth of the probability of mammal death or life span reduction caused by repeated acute and chronic irradiation by different dose rates. Described are present-date estimates of equivalent doses from GCR and SCR behind various shields, and radiation risks for cosmonauts of different age on a mission to Mars. Also compared are values of total radiation risks over the length of life, risks of cancer and lifetime reduction after the planetary mission derived by the mathematical modeling and calculation.

Age Factors↗

PubMed2003

[A model of ecological hazard and social tension for the description of the health deterioration risk in the Russian population].

A model for quantitative evaluation of risks from long-exposure to high-intensity anthropogenic factors and chronic psychoemotional stress is presented. The model has been based on the concept of G. Seliet concerning the development of non-specific physiological reactions (the general adaptation syndrome) to chronic comparatively intensive stresses. It describes the process of time-dependent depletion of the compensatory body reserve and the probability of regulation disorders and disruption of the adaptation to single factors or their combinations. On the population level, health risks predicted with the model are growth of death probability within a year and in a delayed period (transformation of age-specific coefficients of mortality) and a magnitude of reduction of remaining life expectancy.

Adaptation, Psychological↗

PubMed2003

[Chronic psychoemotional stress and its effect on population health].

Consideration is given to the quantitative characteristics of health effects of the chronic psychoemotional stress associated with the economic and social status of one's family, and profession. The study was performed with the use of a model of decline in the human body compensatory reserve on a background of single or combined stresses. On a population scale, this can be seen in a regular growth of the death coefficient in various age groups and an increase of the mean death coefficient in regional and whole country populations. Analyzed were the psychoemotional and health implications of the level of per capita income in a family with full employment of able to work members, unemployment, some natural disasters, and type of occupation. Ageing and death coefficient trends in several regions of the country were correlated on a basis of the analysis of single and combined chronic effects of radiation, chemical pollution, altered economic and social status, and type of occupation. The author speculates on changes in morbidity, total risk of death and possible reduction of the life expectancy caused by the multitude of the above-mentioned negative factors.

Aging, Premature↗

PubMed2002

Lifetime total radiation risk of cosmonauts for orbital and interplanetary flights.

This paper presents results of calculations of total radiation risk for cosmonauts over their lifetimes and assessments of possible shortening of life expectancy on the basis of generalized doses calculated for cosmonauts after a long term interplanetary and orbital space missions on "MIR" station and International Space Station with the use of mathematical expressions coming from a model of change mortality rate of mammals after irradiation. Tumor risk assessments for cosmonauts over lifetime after flights are also given. Dependences of the delayed radiation consequences mentioned above on flight duration, spacecraft shielding thicknesses, solar activity and cosmonauts' age are analyzed.

Age Factors↗

PubMed2002

Estimation of a cosmonaut's radiation hazard during long-term space missions on the basis of a generalized dosimetric function.

This paper presents a new concept of radiation hazard assessment for spacecraft crew members during long term space missions on the basis of a generalized dosimetric function. This new dosimetric function enables a complicated nature of space radiation exposure to be reduced to the conditions of a standard irradiation. It can be obtained on the basis of mean-tissue equivalent dose values calculated for each space radiation source and transmission coefficients describing the influence of the complex spatial and temporal distribution of the absorbed dose in the cosmonaut's body on the radiobiological effects. The combination of cosmic ionizing radiation with other non-radiation nature factors in flight can also be accounted for. In terms of the generalized dose, it is possible to assess the nature and extent of lowering a crew working capacity, as well as radiation risk, both during a flight and post flight period.

Aerospace Medicine↗

PubMed2002

[The assessment of radiation hazards in the "MIR" and ISS orbits from the data of vehicle and personal dosimetric monitoring].

The paper describes the procedure of estimating total radiation risk to crewmembers during lifetime and possible lifetime reduction in consequence of participation in the Mir and ISS missions in different periods of the solar activity. The procedure includes analysis of data of vehicle and personal dosimetry, and calculations of radiation doses in various Mir compartments and accumulated by body tissues of cosmonauts. Calculated doses showed good consistency with the doses measured with R-16 on board Mir and personal dosimeters. To a first approximation, estimation of doses to cosmonauts and radiation risk as a result of participation in ISS missions took into account similarity of the Mir and ISS basal modules (geometry, dimensions and mass values) and was performed with the use of the space station shielding model that had been described elsewhere. The model of ISS radiation shielding will be updated as data of dosimetry of ISS compartments and phantom studies are available.

Astronauts↗

PubMed2001

[Prediction of the body resistance to chronic irradiation by different dose rates using the generalized logarithmic index].

Patterns of radiation damage development and reparation of the blood-forming system in mice and rats were outlined from calculated values of the generalized logarithmic index for chronic irradiation by different dose rates. Dynamics of the generalized index in the course of chronic irradiation makes the basis for predicting deviations in the resistance of animals during next irradiation session.

Animals↗

PubMed2001

[Levels of radiation exposure and radiation risk in flights aboard the orbital complex "Mir" and the International space station].

The paper presents results of calculating mean daily values of absorbed and equivalent doses from galactic cosmic rays (GCR) and Earth's radiation belts (ERB) to crew members on orbital missions aboard Mir and the International space station during solar minimum and maximum. Calculated doses were corrected in accordance with the dosimetric and spectrometric data from Mir missions 18 through to 23 that took place in the period of solar minimum. Contribution of local and albedo neutrons to equivalent dose was also taken into account. Presented are calculated total radiation risk and tumor risk over life time for Mir and ISS crews following missions of varying duration, and predictions for reduction in life span in view of recent dosimetric data.

Adult↗

PubMed2000

[Radiation risk of malignant tumors in cosmonauts over life time as a result of participation in interplanetary and orbital missions].

The paper considers model concepts of cell blast-transformation and oncogenesis in humans consequent to ionizing irradiation with varying dose rates and lengths of exposure. Presented are data of epidemiologic studies of oncologic risks for different organs and body tissues at different ages in a year since exposure calculated per a unit of absorbed dose (1 cGy). Probability of tumor development in males of different age due to chronic irradiation of various lengths was determined per a dose unit. Based on these data and with regard for possible dose loads on interplanetary and orbital crews, oncologic risk for cosmonauts was calculated in terms of life time. The dependence of radiation-induced oncologic risks on type and duration of space mission, shielding thickness, and solar cycle was analyzed. The authors compare values of the total radiation risk and oncologic risk for cosmonauts launched at various ages.

Astronauts↗

PubMed2000

[Probability of lens opacity and mature cataracts due to irradiation at various LET values].

The paper reviews experimental and clinical data on the incidence of opacity of the lens and cataract development in animals and humans due to exposure to different types of radiation. Cataractogenous effectiveness of fast neutrons, accelerated ions of carbon, helium, neon and argon with the energy of 300 MeV/nucleon, and 137Cs gamma-radiation was compared. Analysis of the incidence of opacity of the lens in consequence of low doses gave high RBE estimates (from 10 to 40). The extremely high cataractogenous effectiveness of accelerated ions makes on thing that the existent space radiation limits, particularly in part of the GCR effects on the lens and permissible doses for cosmonauts, should be reconsidered towards mitigation. The authors discuss issues of threshold radiation doses that do not markedly increase incidence and rate of the lens opacity development in the post-exposure period.

Animals↗

PubMed2000

[Method of integral evaluation of alterations in the body systems due to various factors on the basis of generalized parameters].

The paper presents generalized parameters for quantitative evaluation of shifts in human health and separate body systems due to external factors based on available circumstantial data of prophylactic medical examination of different cohorts of population and professional groups. Test of the generalized logarithmic parameter proved its applicability to the quantitative evaluation of radiation damage to and recovery processes in the blood-forming system following repeated acute exposures. A significant fall in the rate of recovery of the system and increases in the number of fractions and the total absorbed dose were demonstrated.

Adolescent↗

PubMed2000

[Delayed effects of ionizing radiation on the skin as a function of dose].

The article contains analysis of experimental and clinical data on delayed effects of different doses of ionizing radiation on the skin which in the row with the bone marrow, lens and other radiosensitive organs and critical tissues is one of the criteria of radiation risk for cosmonauts. According to the existing standard, maximal dose to the skin over the career may not exceed 1200 cSy. However, facts presented in the article testify the necessity to reform the standard since there is high probability of pathology including malignant tumor in delayed period after exposure to 1200 cSy. In view of the available data and present-day international recommendations, the maximal dose to the skin over the space career should not be higher than 600 cSy.

Basal Cell Carcinoma↗

PubMed1999

[Methodical approaches for establishing the values of spatial non-uniformity radiation coefficients for generalized dose calculation to evaluate immediate radiobiological effects].

The paper substantiates the key role of hemopoiesis damage in the character and severity of radiation reaction and survivability of the body shortly after exposure. The proposed model of equally effective dose takes into consideration modification of the radiobiological effect by spatial non-uniformity of radiation and allows reduction of the effects of non-uniform radiation to the standard uniform radiation. Described is the algorithm for calculating values of the equally effective dose and coefficients of spatial non-uniformity of space radiation required to determine the generalized dose and radiation risk for cosmonauts on extended missions.

Aerospace Medicine↗

PubMed1999

[The methodology of establishing the radiation hazard to cosmonauts on long-term mission based on the generalized dosimetric functional].

The paper describes an original methodology for evaluation of the radiation hazard to cosmonauts on mission based on generalized dose from ionizing radiations. This is a new dosimetric functional that allows convert the complex radiation of space to standard radiation. The conversion is achieved by calculation of mean tissue equivalent doses from each source of radiation hazard in space flight and scaling factors which take into account the radiobiological effect of intricate macrospatial and temporal dose distributions along the human body. Besides, consideration is given for the impact of non-radiation factors inherent to space flight. The generalized dose which is the dose from standard radiation inducing radiation damage similar to the multicomponent space radiation can be used to ascertain the character and degree of performance degradation, and radiation risk for cosmonauts both in and long after mission.

Cosmic Radiation↗

PubMed1999

[The determination of the radiation risk during an interplanetary space flight at different periods of solar activity].

Based on the own algorithm and Fortran calculation program the authors estimated radiation risk to cosmonauts on an interplanetary mission. They also analyzed the dependence of risk values on mission duration, space vehicle shield thickness, solar phase, and cosmonaut's age. The magnitudes of radiation risk to cosmonauts were compared with the national demographic risk of male lethality over a similar period of time.

Adult↗

PubMed1999

[An algorithm to compute the radiation risk during interplanetary space flights].

The algorithm of estimation of the radiation risk to cosmonauts on long-term interplanetary missions stems from new approaches to the estimation of radiation hazard, calculation of generalized dose inputs from various space radiations, hypothesized probability of human death due to exposure to varying doses of standard radiation. These data allow calculation of radiation risk from deterministic sources along the flight trajectory and stochastically distributed in time solar flares. Results of this calculation can be further used to correlate the in-flight radiation risk with mission length, shield thickness, solar cycle, and age of cosmonauts. They may be additionally used to compare the in-flight radiation risk with the national demographic risk of male lethality over a similar period.

Adult↗

PubMed1999

[Radiation risk for astronauts during space flights on board the space station "MIR"].

Described is the algorithm for calculating the radiation risk to cosmonauts on orbital missions during different solar phases. The algorithm and the Fortran calculation program lie in the basis of presented radiation risk estimations for orbital manned missions of varying duration. The dependence of in-flight radiation risk on mission length, solar phase, and cosmonaut's age was analyzed. Magnitudes of radiation risk to cosmonauts were compared with the national demographic risk of male lethality over a similar period of time.

Algorithms↗

PubMed1999

[The model of the rate of radiation-induced mammalian death based on the determination of delayed consequences of different doses of radiation].

Analyzed were model descriptions of the probability of mammalian lethality and a possible life span reduction consequent to acute and chronic exposures to different dose rates. The proposed model of radiation rate of mammalian death links variations of the coefficient of mammalian death due to acute and prolonged radiation exposures with age. Application of the model to relevant experimental data yielded model coefficients for these periods of exposure. The radiation-modified dependence of lethality coefficients on age makes it possible to obtain fairly simple analytical expressions describing the survival probability long after exposure as a function of dose and dose rate, estimating radiation risk at any time point following exposure, and shortening of mean life span associated with exposure to different doses.

Acute Disease↗